IRITIS. A very dangerous disease of the eye, producing inflammation in the iris or coloured circle which surrounds the pupil. Iritis is frequently produced by rheumatism, as well as by scrofula and gout, and often places the sight in great peril.
The symptoms are pains around the ball of the eye and on the brow, which increase at night, cloudiness of the cornea, difficulty, and inequality of contraction in the pupil, change of colour in the iris, frequently disturbed vision, and much pain in and watering from the eye when the patient is placed in the light, particularly a strong light.
We have described the principal symptoms of this serious disorder in order that any one affected by them may at once seek the assistance of a skilful surgeon or oculist.
I′RON. Fe. Syn. Ferrum, L.; Fer, Fr.; Eisen, Ger. The history of this most important
metal extends to the remote past. The discovery of an iron rod in one of the Assyrian bronzes brought to England by Mr Layard established the interesting fact that this metal was known and commonly employed, where strength was required, nearly 3000 years ago. Rust of iron and scales of iron were used as medicines at a period equally remote.
Sources. Iron in a metallic state (native iron) is of very rare occurrence; but it invariably enters into the composition of meteorites. Combined with oxygen and other elements, as iron ores, it occurs in nearly every part of the earth. These ores may be divided into the oxides and the carbonates. The oxides may be again divided into four distinct classes, viz.—(1) Magnetic iron ore, consisting of 31% protoxide and 69% sesquioxide, with an insignificant proportion of silica; (2) specular iron, or iron glance, composed of the sesquioxide, with a small admixture of magnetic oxide; (3) red hæmatite, consisting of the sesquioxide nearly in a state of purity; and (4) brown hæmatite, the hydrated sesquioxide of iron. The carbonates are principally two, viz.—(5) spathose iron, the protocarbonate of iron in a sparry condition, and (6) clay ironstone or black band ironstone, which consists of the protocarbonates associated with clay and carbonaceous matter.
Swedish iron is made almost entirely from No. 1, which occurs in massive beds at Arendahl and Dannemora, in Sweden. This iron is of great purity, being perfectly free from sulphur and phosphorus. The titaniferous iron sand found at Taranaki, in New Zealand, consists almost entirely of No. 1 and the metal titanium. No. 2 found principally in the island of Elba, in the form of rhombohedral crystals. The micaceous iron ore found in small quantities in Wales and Lancashire has nearly the same composition, but crystallises in brilliant plates. No. 3 occurs in radiated fibrous masses in different parts of the world. It is found in large quantities in Wales and Lancashire, some of the specimens from the latter locality containing nearly 99% of the sesquioxide. It makes excellent iron. No. 4 occurs in reddish-brown masses of a botryoidal form. It is a valuable ore, and is found in England, Wales, and Scotland. No. 5 is found chiefly at Siegen, in Prussia. No. 6 is the principal ore of the Staffordshire and Scotch iron districts, where it occurs in great abundance, associated with the fuel and the flux required for smelting it. Iron is contained in plants, and forms an essential component of the blood of the higher animals.
Prep., &c. Iron is only prepared on the large scale, and an account of the manufacture would be out of place here. Those requiring detailed information must consult the elaborate works of Percy, Hunt, Fairbairn, Phillips, and other metallurgists.
Pure iron may be prepared by introducing fine iron wire, cut small, 4 parts, and black
oxide of iron, 1 part, into a Hessian crucible; covering with a mixture of white sand, lime, and carbonate of potassium (in the proportions used for glass-making); and, after applying a closely fitting cover, exposing the crucible to a very high degree of heat. A button of pure metal is thus obtained, the traces of carbon and silicon present in the wire having been removed by the oxygen of the black oxide.